America's attention may have moved on from Afghanistan to Iraq, but Thursday's violence in Kabul and Kandahar is a stark reminder that its work there is far from over. A car bomb explosion in the capital killed at least 10 people, while a few hours later in Kandahar, President Mohammed Karzai survived an assassination attempt by a shooter in Afghan army uniform. These were hardly isolated incidents: Thursday's bombing was the eighth in the capital in less than a month, and Karzai's deputy, Haji Abdul Qadir, had been assassinated there in July  prompting U.S. personnel to take over the president's security. The mounting campaign of bombings and ambushes of government and U.S. targets over the summer underscore not only the fragility of the U.S.-backed Karzai regime, but also a resurgent anti-American guerrilla campaign by forces including, but not confined to the Taliban and al-Qaeda.

The attacks follow public statements by elements close to al-Qaeda and the Taliban promising a new guerrilla campaign against the U.S. and the Karzai government. Earlier this week, the notorious Pashtun warlord Gulbuddin Hekmatyar declared a 'jihad' for the ouster of foreign forces from Afghanistan. With Karzai's authority limited to the capital, much of the countryside in the hands of fickle warlords and many Pashtuns suspicious of the disproportionate dominance of ethnic Tajiks in his government, the remnants of the Taliban may be finding fertile ground for a resurgence. Beside the bomb blasts and assassination attempts in the capital, there has been a steady stream of direct attacks on U.S. bases and patrols in different parts of the country.

[an error occurred while processing this directive]The Taliban may have been forced to surrender its grip on Afghanistan's cities last winter, but it was never systematically disarmed. Its fighters simply scattered into the hills, returning to their villages and, in many cases, joining up with local warlords. Many of their leaders escaped capture, too, most notably the one-eyed peasant mystic Mullah Omar  who has eluded capture by the U.S. despite the widespread belief that he remains based in the mountains of his home province. And the shape of the post-Taliban order in Kabul may have paradoxically helped set the stage for a Taliban resurgence.

The primary beneficiary of the Taliban's rapid collapse had been the ethnic-Tajik "Pansjiri" faction of the Northern Alliance, the main U.S. proxy force which seized Kabul last Fall (against Washington's wishes) and became the dominant component of Karzai's government (much to the president's discomfort, although their power on the ground  and the reluctance of the U.S. to challenge it  leaves him little choice). Despite his own Pashtun roots, Karzai's ability to secure support in his heartland is imperiled by the disproportionate Tajik power in Kabul. That suits his Pashtun enemies: Since the Spring, the Taliban, al-Qaeda and Hekmatyar have all sought to foment a new 'jihad' against Karzai and the U.S. by exploiting Pashtun alienation from the Tajik-dominated government. That, and the vicious rivalry among local warlords  some of whom have been anointed as regional chieftains by the new government or been financed and armed by the U.S. for proxy service in the hunt for al-Qaeda  has helped those looking to direct the energies of many Afghan career-warriors into a campaign against Kabul. Incidents such as the accidental U.S. bombing of a wedding party in Oruzgan also appear to have been exploited to spread anti-Karzai sentiment in the Pashtun heartland.

Reports have suggested variously that Iran continues to back Herat warlord Ismail Khan (hardliners in Tehran may even be assisting Hekmatyar, despite his expulsion by the government in February), that Russia is backing the Pansjiris and that elements in Pakistan may be harboring Taliban and al-Qaeda elements to make their own proxy bid for power in Kabul if the U.S. begins to withdraw.

Skepticism over the durability of Karzai's regime is hardly surprising, since for months it has been apparent that his power is almost entirely derived from the presence of foreign armies  the U.S. special forces and air power that put the Taliban to flight and keeps more ambitious warlords in their place, and the International Security Assistance Force composed primarily of European troops (currently led by Turkey). And the reluctance of the U.S. to sanction any expansion of the peacekeeping mission beyond the 4,000 ISAF troops currently in the capital has earned Karzai the unkind nickname "Mayor of Kabul," since his writ doesn't run much beyond the city limits. Even there, some U.S. foreign policy experts believe he's in danger both from the Pansjiris and from the increasingly confident anti-Karzai jihadis.

Although a desire to speed the extraction of U.S. troops from Afghanistan had prompted the Pentagon to oppose expanding Karzai's defense, that position may be shifting. U.S. officials now speak favorably of a more extensive ISAF, although no U.S. troops or funds would be offered for the task. And the challenge facing any larger peacekeeping force is plain, because the U.S. and its allies have plenty of enemies in the Afghan countryside. It's hardly surprising, then, that there's no rush to join. Indeed, allies opposed to a U.S. invasion of Iraq are likely to point to the deteriorating security situation in Afghanistan as grounds for caution.

Karzai's U.S. security detail kept him alive this time, dispatching his would-be killer within seconds. But it was the second credible attempt on Karzai's life in as many months. Keeping Karzai in power  and the Taliban-al Qaeda elements at bay  looks increasingly dependent on substantially expanding the presence of coalition troops. And on the U.S. and its allies getting far more deeply involved in the messy violence of Afghan politics than they had ever intended.